1. Technical Field
The present invention relates to a robotic device, a method for controlling a robotic device, and a computer program.
2. Related Art
A robotic device having a multijoint structure is often used as a part of an IC handler or an assembling device and has been in heavy usage in a variety of industrial fields. Therefore, the speed and accuracy by which the robotic device can move an arm to a desired position has been a particularly important performance characteristic of such robotic devices.
In general, to move an arm quickly and accurately, it is preferable to reduce the inertial force acting on the arm and to prevent a load for a driving actuator from increasing. To reduce the inertial force acting on the arm, reducing the arm weight has been the most effective measure. However, the reduction of the arm weight results in a reduction in the rigidity of the arm. This causes a problem in that it becomes difficult to suppress vibrations of the arm when the arm stops. Even if a tip portion of the arm is stopped at a target position, a displacement corresponding to the amplitudes of the vibration of the arm itself is caused. Therefore, a subsequent action is not allowed to start until the vibration is sufficiently attenuated.
To cope with this problem, there have been proposed, for example: a method for disposing an acceleration sensor at a tip of an arm to operate the arm based on an acceleration signal, thus suppressing vibrations (e.g., JP A 1-173116); and a method for disposing an angular velocity sensor at a tip of an arm and the arm itself to thereby control the arm operation based on the angular velocity signal (e.g., JP A 2005-242794).
However, since the control signal for suppressing the vibrations is generated using either the angular velocity sensor or the acceleration sensor in the above methods for controlling the robotic device, if an error such as bias drift is included in the sensor signal, an error is caused in the control signal. Thus, accurate control might fail to be achieved in some cases.
In the above JP A 2005-242794, for example, since two types of filters, namely a low-pass filter for eliminating a high-frequency component of the angle sensor and a high-pass filter for eliminating a low-frequency component of the angular velocity sensor, are used in order to reduce the influence of an error of each of the sensors, the amount of operations performed in a control device increases. Thus, there is a problem that too much time is consumed for processing, or costs are increased for an arithmetic device to increase processing speed.